Electronic organs have been known for many years. Early electronic organs used various electrical-mechanical devices for generating electrical oscillations corresponding to musical tones. Various types of electronic oscillators have also been used to provide such oscillations. Some organs have used an independent oscillator or generator for each tone. In the past the use of such independent oscillators has been quite expensive, and for cost saving reasons it has become common practice to provide twelve oscillators to provide the semitones of the top octave, and to use divide-by-two circuits to porvide the tones in lower octaves. More recently it has become well known to use a single radio frequency oscillator with divider circuits of different divider ratios to produce the top octave of tones. This system is sometimes known as a top octave synthesizer (TOS). Strings of divide-by-two circuits have been used to provide the notes in lower octaves of the organ.
With the advent of reliable large scale integrated circuit (LSI) chips efforts have been made to construct electronic organs utilizing digital circuits. It is relatively easy to construct LSI chips that will handle digital circuits whereas it is relatively very difficult to utilize analog circuits with such LSI chips.
With a top octave synthesizer approach all of the generators or oscillators have in most instances been locked together is predetermined relation, due to their operation by the single radio frequency oscillator. The approach of utilizing twelve oscillators with divide-by-two circuits has avoided locking notes together within an octave, but has caused octave locking.
The patent art has recognized the undesirability of octave locked oscillators. For example see Eugene S. Morez U.S. Pat. No. 3,828,109. Certain of the claims of this Morez patent were lost to Dale M. Uetrecht pending application for U.S. Pat. Ser. No. 563,431, filed Mar. 31, 1975, and now U.S. Pat. No. 4,056,995. During the interference proceeding Uetrecht was accorded the benefit of his earlier U.S. Pat. No. 3,816,635, and attention therefore should be directed to both Uetrecht patents. The work of both Uetrecht and Morez appears to have been based on an article "Many Digital Functions Can Be Generated With A Rate Multiplier" by Richard Phillips published in Electronic Design Magazine dated Feb. 1, 1968, pages 82-85. Both Uetrecht and Morez adopted a policy of dividing by some factor not quite equal to two in order to unlock footages of notes that would otherwise have exactly a two to one relation.